Isthmic Lumbar Sacral Spondylolisthesis in Adults

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Spondylolisthesis occurs when one lumbar vertebra slips forward in relationship to the adjacent vertebra. In the Greek language, the term spondylolisthesis means slipped vertebra. The neural arch (lamina) and the paired facet joints are anatomical structures that prevent vertebrae from slipping (Fig 1).

posterior spinal elements

Figure 1. Posterior elements of the spine.
The neural arch (lamina) is located in the middle,
between the facet joint complex. Photo Source:

A vertebra may slip following the development of a stress fracture through the neural arch. The defect in the lamina separates the back part of the vertebra from the remaining part; the vertebral body and disc. The stabilizing role of the paired facet joints is lost and the vertebral body slips forward. The laminar stress fracture (in Greek called spondylolysis) occurs in a specific region of the lamina called the pars interarticularis or isthmus. Hence the condition is called isthmic spondylolisthesis (Fig 2).

Figure 2. Isthmic Spondylolisthesis.
Photo Source:

In some cases, the stress fracture occurs in early childhood and by age-six spondylolysis has developed. Incidence of this is found in about 4.4% of the population. In many cases the stress fracture does not cause any symptoms or discomfort and goes unrecognized.

The actual vertebral slip (spondylolisthesis), as a result of spondylolysis develops later on in life, somewhere during adolescence. In adults, the incidence of spondylolisthesis is about 6%. In rare cases, the slip may develop later in adult life (e.g. after age 20).

In the vast majority of cases, isthmic spondylolisthesis occurs at the junction of the lumbar spine and the sacrum (pelvis). In medical terms, this junction is the L5-S1 level, which is between the 5th lumbar vertebra and the 1st sacral vertebra. There seems to be a genetic predisposition to the condition. In some cases, several of the patient's family members may have acquired spondylolisthesis.

Commentary by: David S. Bradford, MD

Isthmic spondylolisthesis is an important cause of back pain and disability in children, adolescents, and adults. The natural history and clinical presentation of isthmic spondylolisthesis is distinct from other etiologies of spondylolisthesis. Dr. Floman has made an important contribution to our understanding of isthmic spondylolisthesis in adults by demonstrating a significant incidence of deformity progression in adulthood, and suggesting a mechanism to explain the variable onset of pain associated with spondylolisthesis in adults. (1) Operative management in the patient with symptomatic isthmic spondylolisthesis is clearly superior to non-operative care. (2) However, there remains significant variation in surgical strategies, and limited evidence to guide decision-making.

In low-grade isthmic spondylolisthesis, the role of anterior column support has not been well-defined, and there is little consensus on circumferential arthrodesis compared with posterolateral fusion alone. In fact, a beneficialeffect of instrumentation has not been clearly established in these cases. (3) In contrast, in grade 3 and 4 spondylolisthesis, there is strong evidence to suggest improved rates of arthrodesis and better clinical outcome with structural support of the anterior column. (4) In high-grade spondylolisthesis, partial reduction and transosseous fixation has resulted in reliably good clinical outcomes. (5) The role of complete reduction and restoration of lumbopelvic relationships remains to be established.

Dr. Floman's observation that the surgical treatment of symptomatic isthmic spondylolisthesis is a reliable procedure for the treatment of pain and dusfunction is confirmed by our published and unpublished data. (5,6,7) Further investigations including multicenter prospectve clinical studies are required to establish an evidence-based consensus approach regarding the role of interbody arthrodesis in low-grade spondylolisthesis, the role of reduction of slippage and restoration of lumbosacral lordosis in high-grade spondylolisthesis, and the role of in-situ arthrodesis in adults.

  1. Floman, Y. Spine. 2000;25(3):342-7.
  2. Moller H, Hedland R. Spine. 2000;25(13):1711-5.
  3. Moller H, Hedland R. Spine. 2000;25(13):1716-21.
  4. Molinari RW, et al. Spine. 1999;24(16):1701-11.
  5. Smith JA, et al. Spine. 2001;26(20):2227-34.
  6. Bradford, DS. J Bone Joint Surg Am. 1990;72(7):1060-6.
  7. Butterman GR, et al. Spine. 1998;23(1):116-27.

Updated on: 08/01/19
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Isthmic Spondylolisthesis and Degenerative Spondylolisthesis
David S. Bradford, MD
Professor and Chair Emeritus
UC San Francisco
Department of Orthopaedic Surgery
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